Lighting control circuits



Sept. 27, 1960 G, C, 1ZENOUR 2,954,509

LIGHTING CONTROL CIRCUITS Filed April 22. 1958 BY {,L/ ZL v 4 fro@ ys United States Patent 8 'Claims'. (Cl. 3154-199) Conn., assignor to Cen- New York, N.Y., a corporation This invention relates to electric lighting control Vcircuits, and, more particularly, to circuits of the type which find their greatest use in theater and television lighting.

The present invention constitutes a modification of the lighting control circuits shown, described and claimed in my reissue United States Letters Patent Re. 231,575, reissued Novernber'll.,- 1952 for Lighting Control Circuits.

It will be observed' that the arrangements shown in my aforesaid patent provide a comparatively complex circuit arrangement that utilized a substantial number of componentsfo presets, lfading and individual controls. This type of circuit is necessary for large and elaborate establishments, as for instance, in major' Vtelevision studios and Broadway theaters. To accomplish the degree of ilexibility and selectivity that is a requisite for such operations, agreat number of controls are needed. However, where 'the' demands are less" exacting, as for instance, in. local television studios and non-commercial theaters, eg. school theaters, it is highly desirable to provide a far less complex and inexpensive arrangement.

It is an object of the present invention to provide such ai simplified arrangement which does away with a large number of control elements and with many other elements as welll in order to simplify the operation and lower fthe` oost of a lightting control circuit of the character described..

. It is another object of my invention to provide a light,- ingcontrol circuit of the character described which, although not achieving the smoothness of operation and changeover which my saidl reissue patent, nevertheless provides an `operation which is satisfactory for installations such as public and high school auditoriums, little theaters, off-Broadway productions and local television studios.

Other objects of my invention in part will be obvious, and in part will be pointed out hereinafter.

My invention accordingly consists in the features of construction, combinations of elements and arrangements of parts which will be exemplified in the lighting control circuit" hereinafter described and of which the scope of applicationl will be indicated in the appended claims.

`11n the accompanying drawingl have shown a wiring diagram for a lighting control circuit embodying a preferred form of my invention.

In said diagram the reference numeral 10 indicates a p'air of lamps connected in series, these being exempliilcative of the lighting load to be controlled by the circuit. Said lamps are energized from a pair of alternating current bus lines, to wit a hot bus 12 and a neutral bus 14. The lighting control circuit essentially conipses two sections, one of these being the control end where low voltages' prevail and the other the power unit where a line or a higher voltage is present. f

The control end includes an` auto-transformer 16 which draws its-power from the busses 12, 14. Said autotransformer includes a variable tap 18 adapted' t"o sweep across the cntirewindingof the transformer so that the is an attribute of the circui-t shown in '2,954,509 Patented Sept. 27, 1960` 2 former can be shorted or fully energized. For reasons which later will be apparent, this transformer is sometimes referred to as the fading transformer. The primaries 2'0, 22 of a pair of step-down transformers 24, 26 are connected in series across the Iterminals of the fading transformer. The transformer tap is connected to the junction of `said primaries. It will be seen that if the variable tap is in one position, for example, the lowermos-t position in the diagram, the primary 22 of the transformer 26 will 'be shorted out, and the primary 20 of the transformer 24 will be fully energized. Conversely, if the tap is moved to its other extreme position, this be'- ing the uppermost position in the diagram, the primary 20 will be shorted out, and the primary 22 will be fully energized. Y

The secondarie's 28, 30 of the transformers 24, 26 likewise are series connected. From their junction point 32 a lead 34 extends to the junction point 316 between a pair of series connected potentiometers 38, 40. A lead wire 42 connects the other terminal of the transformer secondary 28 to the other terminal of the potentiometer 38 While a lead wire 44 connects the other terminal of the transformer secondary 3'0 to the other terminal of the' potentiometer 40. It now will be appreciated that when the 'fader control 18 is i'n the uppermost position in the diagram, the potentiometer 40 will be energized, while if the fader control is in the lowermost' position in 'the diagram, the potentiometer 38 will be energized. The potentiometer which is not [energized is effectively shorted so lthat the potential at any pointV thereof is the same as at the ends of the potentiometer.. The transition from energization of one potentiometer to` that of the other potentiometer will occurl as the tap 18 is moved from one extreme position to the other, it being 'understood that it is not intended to stop movement of the tap at any intermediate point with both potentiometers partly energized. The function of the fader transforineris to gradually transfer energization from one potentiometer to the other.

It is important to note at this point that the voltage appearing across either potentiometer which is energized is in phase with the alternating current voltage applied to the' busses 12, 14. a

A switch connection is utilized 4to connect the control end of the circuit which has thus far been` described -to the power unit` which soon will be described. Said switch connection includes a' double throw double pole switch 45. Specifically, said switch includes two movable blades 46, 47, a pair of contacts 48, 50 associated with the blade 46 yand a pair of contacts S2, 54 associated with the blade 47. The switch 45 is of a standard type conventionally kno-Wn as a make-before-break switch, that is to say, when -a switch blade moves from one to the other of its pair of associated contacts, it will engage the contact toward which it lis moving before it disengages the contact it is leaving. Therefore, at all times the switch blade is touching one cont-act or another. There is no instant when the switch blade, in its movements between the contacts, engages neither Contact. The construction of such switches is well know/vn,I and, therefore, will not be detailed Iherein. rl'lhe reason for the use of this type of switch will be pointed out hereinafter. The switch blades 46, `47 'are jointly interconnected for com.- mon movement. l

The contact 4S associated with the switch blade 46 is connected by a lead 56 to the Imovable tap of the potent-iotmeter 38. The contact 52 associated 'with the switcl blade 47 is connected by a lead 58 to the movable tap of the potentiometer 40. r[lhe two contacts 48, 52 are so positioned that `when one switch blade engages 011e of lthese contacts, ythe other switch blade will engage the other terminal of said transformer has connected to it a lead 70.

The leads 64, 70 run to a means 72 for providing a lagging voltage, the voltage lag ranging, 'as will be appreciated by those skilled in the art, between about 90 to 180 behind lthe in-phase voltage across the potentiometers 38 or 40 and across the busses 12, 14. Said means is connected in series With the potentiometers and ise'nergizedby a transformer 74, the primary 76 of which draws power from the busses 12,l 14. One secondary winding 78 of the transformer 74 furnishes the energy for the lagging voltage. A potentiometer 80 is connected across the secondary 78, the tap of said potentiometer being connected by a lead 82 to one end of a resistor 84, the other end of which is connected to a capacitor 86 at a junction 88. The other side of the capacitor is connected by a lead 90 to the other end of a secondary 78. The RC pad consisting of the resistor 84 and series connected capacitor 86 provides a voltage which lags behind the .voltage appearing across the potentiometer 38 or 40. The amplitude of the lagging voltage is controlled by adjusting the tap of the potentiometer 80. The resistor 84 is Variable so that the degree of lag can be changed by adjusting the value of said resistance; reducingthe resistance will increase the lag, and viceversa.l The lead 70 is connected to the junction 88 so that when the potentiometers are connected by the switch 42, there will be impressed across the primary 66 of the transformer 68, a voltage which is a vector addition resultant of the in-phase voltage furnished by the pre-set potentiometers 38, 40 and the lagging voltage furnished bythe RC pad just described. In normal operation of the device, the potentiometers are adjusted from time to time in a manner well known, but the lagging voltage, when once set by adjustment of the potentiometer 80 and resistor 84 remains fixed. The settings of these latter two adjustments will be described hereinafter. It will be appreciated that the vector addition of the two mentioned voltages will produce a resultant voltage, the phase angle of which will vary as a function of the amplitude of the in-phase voltage but always will lag to some extent. However, the amount of lag can be re duced to avery small degree or it can be increased to almost 180.

The voltage which is the vector addition resultant will, as noted, be impressed across the prim-ary of the grid transformer 68. A corresponding voltage having the same phase lag with respect to the irl-phase voltage of the busses will be induced across the secondaries 92, 93 of said transformer. The lagging voltage is employed to control the tiring of a pair of backeto-back A.C. phaseresponsive devices constituting thyrat-rons 94, 96. More particularly, a lead 98 runs from the secondary 92 to the grid 100 of the thyratron 94, and a lead 102 runs from the secondary 93 to the grid 104 of the thyratron 96. Each of these leads has interposed therein `a current limiting resistor 106. A lead 1418 from the other terminal of Ithe second-ary 92 runs to the cathode 1.10` of the thyratron 94. Similarly, a lead 112 runs from the other terminal of the second-ary 93 to the cathode 114 of the thyratron 96. The said lcathodes are energized by lil-arnent secondaries 116, 118 on the transformer 74. A lead 120 cross-connects the cathode 114 of the t'hyratron 96 to the anode 122 of the thyratron 94. Similarly a lead 124 cross-connects the cathode 110 of the thyratron 94 with the anode 126 of the thyratron 96. Grid leali capacitors `128 are shunted across the grids yand cathodes of both thyratrons.

A lead 130 connects one side of the lamp load 10 to one cf the busses 14 and another lead 132 connects the other side of the lamp load to the load 124, the lead 132 including a smoothing choke 134. Power is obtained for energization of the lamp load by a booster transformer 136 connected between the busses, the step up terminal of said transformer being connected bya lead 138 to the cross-lead 120.

To follow the operation of the circuit, let it be assumed that the fading transformer tap 18 is in its uppermost position so that the transformer 26 and the potentiometer 40are energized; Let it further be assumed that the switch 45 is in itsuppermost kposition so that the blades 46, 47 engage the contacts 48, 52 respectively. This will cause to be impressed upon the transformer primary 66 a voltage which lags the bus voltage by a certain amount that-is a function of the setting of the p0- tentiometer 40.

Let it also `be assumed that the bus 12 is at the` beginning of its positive half-cycle with respect to the bus 14. During this half-cycle, the anode 126 of the thyratron 96 will be negative with respect to' the cathode 114, so that this thyratron cannot lire. However, in the same halfcycle, the anode 122 is positive with respect to the cathode of the thyratron 94 so that said thyratron is in a conductive half-cycle ready to tire. However, it will not lire unless the voltage on the grid 100 of the thyratron 94 is above threshold value. Since the voltage applied to this grid at the beginning of the conductive cycle is negative, because the voltage induced inthe secondary 92 lags the bus voltage, the thyratron will not fire. However, at a certain point in the conductive cycle, which point will depend upon the setting of the potentiometer 40, the voltage on the grid 100 will reach and start to pass the grid threshold voltage (the larger the in-phase voltage taken from the potentiometer 40 the earlier in the cycle will this point be reached). Then, in a period of a few microseconds, the thyratron 94 will be ionized andV lire.

Current will flow from bus 14 through lead 130, then through the lamp load 10, then through lead V132 and' smoothing choke 134, then through cross-lead 124 to the bus 14, the thyratron 96 enters its conductive cycle inasf much as at such time the anode 126 of the thyratron 96 is positive with respect to the cathode 114 of said thyratron.V I Once more, firing will not immediately start because the grid Voltage applied by thev secondary 93;

lags the bus voltage so that the grid Voltage has not yet.

reached and exceeded the threshold value. But, as soon as the cycle has advanced far enough for the applied grid voltage to exceed threshold value, this depending upon the setting of the potentiometer 40, the thyratron 96 will lire.

Now, current will flow from bus 14 through lead 130 and the lamp load 10 along the lead 132 through the choke 134 to the anode 126 of said thyratron 96, then through said thyratron to the cathode 114 alongA leads and 138 to the booster transformer 136 and out tobus 12.

The next normal step in operations, when the scene beinglighted requires it, will be to shift the tap 18 to its lowermost position on the fading auto-transforrner 16- so as to decrease energization of the potentiometer 40 to zero and concurrently increase energization of the` potentiometer 38 to its maximum. This places both thyratrons under the control of the potentiometer 38, andy 40 the tap thereof can be moved. thereby to secure manual l regulation of the lighting, 1`oad. a`t.such time if so desired..

When the lighting load is to be blacked out temporarily,

while the thyratrons stillhave.linevoltage'appliedtheretm. 1 the switch 45 is moved toits lowermos'tposition in which the blades 46, 47 engagetheY contacts 50, S4 respectively. In this position, the cross-lead` 60 shunts:` the leads `62, 64 so that only the lagging` voltage. taken fromv the terminals of the resistor .84 is applied. tothe transformer primary v66. insures thata negativ@v ile., turn-off', voltage will appear on the grids of the thyratrons during` their conductive half-cycles so that the lamp load will be completely deenergized.

It will be recalled that the switch 45'i`s of the makebefore-break type so that as it is moved from the rst o'f the positions described above tothe second, the shorting cross-connection 60 will be made` before voltagefrom the control potentiometers 38, `40 is released. This insures immediate blacking out of theY lamp load as` the switch 42 is thrown into black-out position. Similarly, when the switch is thrown to on position, the voltage of Ywhichever potentiometer 38, 40 is energized will be applied to the leads 62, 64 at the very instant the crossconnection 60 is broken. Thus, the lamp load will immediately be changed from blackout `to-controlled illumination intensity. Particular attention has been drawn to this arrangement inasmuch as if the switch were not of the make-before-break type there would be a transition period as the blades 46, 47 were moving from one contact to another when no voltage would be applied across the primary 66. During such interval the thyratrons would tire over their conductive half-cycles inasmuch as the threshold voltages for the grids of these tubes is slightly negative. This would mean that when the switch 45 either moved from controlled energization to black-out, or from black-out to controlled energization, the lighting load would momentarily brighten to full intensity and create a most undesirable elect on the scene being illuminated.

It thus will be seen that I have described a lighting control system. which achieves the several objects of my invention and is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying diagram is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention I claim as new and desire to secure by Letters Patent:

1. An electric lighting control circuit comprising means to supply a selectively variable voltage for controlling intensity of lighting as a function of said voltage, a power unit having a control terminal and adapted to energize a lighting load, means supplying a turn-olf voltage, and make-befoi'e-break switch means for selectively applying either the control voltage or the turn-oli voltage to said terminal.

2. An electrical lighting control system comprising two manually controllable variable voltage dividers, an A.C. source of power supply, means to energize said voltage dividers from said power source to supply from said voltage dividers voltages of variable amplitude of the same wave form as and in phase with the voltage supplied from said source, said energizing means having a manually operable control element for gradually transferring energization from either to the other of the variable voltage dividers, an A.C. phase-responsive device having a control terminal aud adapted to regulate energization of a circuit means to add the lagging voltage and the voltage supplied by whichever of the voltage dividers is energized` and to apply the resultant voltage to the control terminal..

3. An 'electrical lighting control system comprising` l. two` manually controllable variable voltage dividers, an

A.C. source of power supply, means to'energize said voltage dividers from said power source to supply fromlsaid voltage dividers voltages of variable amplitude of the same-waveform -as and in phase with the voltage supplied;

from said source, said energizing means having a manuging 4in phase with respect to the voltage supplied from ally operable control element for gradually transferring` energization from either to the other of the variable voltage dividers, an A.C. phase-responsive device having a` control terminal and adapted to regulate energization of a lighting: load from and in phase with said source, means'` independent of said voltage dividers to supply a single A.C. voltage of selectively variable magnitude andA of a` wave form similar and lagging in phase with respect to the voltage supplied from said source, and circuit means toA addthe lagging voltage and the voltage supplied by whichever of the voltage dividers is energized andto apply the resultant voltage to the control terminal.. 4

4. An electrical lighting control system comprising two manually controllable variable voltage dividers, an A.C. source of power supply, means to energize said voltage dividers from said power source t0 supply from said voltage dividers voltages of variable amplitude of the same wave form as and in phase with the voltage supplied from said source, said energizing means having a manually operable control element for gradually transferring energization from either to the other of the variable voltage dividers, an A.C. phase-responsive device having a control terminal and adapted to regulate energization of a lighting load from and in phase with said source, means independent of said voltage dividers to supply a single A.C. voltage of a wave form similar and selectively variably lagsaid source, and circuit means to add the lagging voltage and the voltage supplied by whicheverl of the voltage dividers is energized and to apply the resultant voltage to the control terminal.

5. An electrical lighting control system comprising two manually controllable variable voltage dividers, an A.C. source of power supply, means to energize said voltage dividers from said power source to supply from said voltage dividers voltages of variable amplitude of the same wave form as and in phase with the voltage supplied from said source, said energizing means having a manually operable control element for gradually transferring energization from either to the other of the variable voltage dividers, an A.C. phase-responsive device having a control terminal and adapted to lregulate energization of a lighting load from and in phase with said source, means independent of said voltage dividers to supply a single A.C. voltage of selectively variable magnitude and of a wave form similar and selectively variably lagging in phase with respect to the voltage supplied from said source, and circuit means to add the lagging voltage and the voltage supplied by whichever of the voltage dividers is energized and to apply the resultant voltage to the control terminal.

6. An electrical lighting control system comprising two manually controllable variable voltage dividers, an A.C. source of power supply, means to energize said voltage dividers from said power source to supply from said voltage dividers voltages of variable amplitude of the same wave form as and in phase with the voltage supplied from said source, said energizing means having a manually operable control element for gradually transferring energization from either to the other of the variable voltcontrol terminal and adapted to regulate energization of a lighting load from `and in phase with said source, means independent of said voltage dividers to supply a single A.C. voltage of a wave form similar and lagging i-n phase with respect toV ther voltage supplied from said source, circuit means to add the lagging voltage and the voltage supplied by whichever of the voltage dividers is energized, and make-before-break switch means for selectively applying either the resultant voltage or the lagging voltage to the control terminal.

7. An electrical lighting control system comprising two manually controllable variable voltage dividers, an A.C. source of power supply, means to energize said voltage dividers from said power source to supply from said voltage dividers voltages of variable amplitude of the same wave form as and in phase with the voltage supplied from said source, said energizing means having a manually operable control element for gradually transferring energization from'either (to the other of t-he variable voltage dividers, an A.C. phase-responsive device having a control terminal and adapted to regulate energization of a lighting loadk from and in phase with said source, an R.C. pad, means to energize said pad from said source so as to provide a single A.C. voltage of a wave form similar and lagging in phase with respect to the voltage supplied from said source, means series-connecting the resistor of said R.C. pad with whichever Voltage divider is energized, so as to create a resultant voltage which lags as a function of the. amplitude of the volt-age supplied by \\(hicl1ever` voltage divider is energized, and means to apply said r sultant voltage to the control terminal.

8. In an electrical lighting controlsystem wherein a lamp load has the energization therof from an A.C. source lamp load has the energization 'thereof from an A.C. source of power supply regulated by 'an A.C. phase-responsive device having a control terminal; that improvement comprising means to supply a pair of selectively en- References Cited in therle of this patent UNITED STATES PATENTS Re. 23,575 Izenour Nov. 11, 1952 ,513,370 Steinmetz Jan. 23, 1894 2,004,613A Meacham .Tune ll, 1935 2,681,428 Rockafellow June 15, 1954 2,786,967

Kuenning Mar. 26, 1957 

